For many electronic devices, particularly small hand-held devices, there is a desire to make the devices as small as possible. This means that it is important for batteries used in battery-operated devices to also be as small as possible. At the same time, device users wish to minimize the frequency with which the batteries must be replaced. Consequently, there is an ongoing need to provide small batteries with higher energy efficiency. At the same time, minimizing the battery cost is a goal.
The energy efficiency of electrochemical battery cells can be maximized by minimizing the number of cell components and the volume of each to provide as much internal cell volume as possible for active materials and electrolyte. One approach has been to use a cell housing with electrically conductive housing members in direct contact with the cell electrodes as the battery terminals. A seal member such as a gasket or grommet is often used to electrically insulate the two battery terminals and provide a compressive seal therebetween. Examples of such cell designs are found in typical button and coin cells, as well as somewhat larger cells.
To achieve a good, reliable seal that is resistant to electrolyte leakage, moisture loss, air ingress and so on, the electrically conductive housing members must have sufficient strength to prevent damage when cell closing forces are applied during cell manufacture and maintain a compressive force on the seal member during cell storage and use. In general, the more massive the housing members, the stronger they are, but less internal cell volume is available. Stronger materials are often more expensive, and material choices are also limited by other requirements, such as resistance to corrosion from internal cell ingredients and the external cell environment.
In view of the above, it is desirable to provide an electrochemical battery cell with an increased internal volume for the electrodes and electrolyte, having a housing made from a conductive material of reduced thickness and sufficient strength to provide an excellent seal. It is further desirable to provide an electrochemical battery cell with improved sealing characteristics and excellent leakage resistance.